Seasonal variation in the invertebrate community and diet of a top fish predator in a thermally stable spring
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PRIMARY RESEARCH PAPER
Seasonal variation in the invertebrate community and diet of a top fish predator in a thermally stable spring Agnes-Katharina Kreiling . Eoin J. O’Gorman . Snæbjo¨rn Pa´lsson . ´ lafsson . Bjarni K. Kristja´nsson David Benhaı¨m . Camille A. Leblanc . Jo´n S. O
Received: 7 January 2020 / Revised: 28 August 2020 / Accepted: 7 September 2020 Ó The Author(s) 2020
Abstract Many life-history events in aquatic invertebrates are triggered by seasonal changes in water temperature, but other ecological factors may be important as well. To rule out the confounding effects of changing water temperature, we studied the seasonal dynamics of an aquatic invertebrate community and their effect on a top fish predator in a thermally stable freshwater spring in South Iceland. We sampled benthic invertebrates five times over a year and conducted a mark-recapture study on the top predator in the system, small benthic Arctic charr, Salvelinus alpinus (L.). We assessed variation in diet composition and feeding preferences by calculating the electivity and individual specialisation of each fish
at each sampling time. There was a clear separation of winter and summer communities for the benthic invertebrates. The variation in prey availability was also reflected in the fish diet, with higher feeding selectivity in summer than in winter for the highly abundant Chironomidae larvae. In contrast, individual specialisation as a measure of intrapopulation niche variation was higher in winter when prey availability was lower. We furthermore found that groundwater amphipods might play an important role in the winter diet of spring-dwelling Arctic charr. In conclusion, seasonal variation in the invertebrate community is an important factor to consider and has the potential to alter the phenotype (e.g. growth rates) and behaviour (e.g. feeding preferences) of higher trophic levels.
Handling editor: Katya E. Kovalenko
Keywords Feeding selectivity Individual specialisation Arctic charr Salvelinus alpinus Phenology
A.-K. Kreiling (&) D. Benhaı¨m C. A. Leblanc B. K. Kristja´nsson Department of Aquaculture and Fish Biology, Ho´lar University, Ha´eyri 1, 550 Sauða´rkro´kur, Iceland e-mail: [email protected] A.-K. Kreiling S. Pa´lsson University of Iceland, Institute of Life and Environmental Sciences, Askja, Sturlugata 7, 101 Reykjavı´k, Iceland E. J. O’Gorman School of Life Sciences, University of Essex, Wivenhoe Park, Colchester CO4 3SQ, UK ´ lafsson J. S. O Marine and Freshwater Research Institute, Sku´lagata 4, 101 Reykjavı´k, Iceland
Introduction Temperature determines the metabolic demands of all ectothermic organisms (Brown et al., 2004). Water temperature is thus a crucial factor shaping individual life-histories, community composition, and food webs in freshwater ecosystems. Seasonal temperature change is a cue that triggers life-history events in many aquatic invertebrates (e.g. emergence and
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Hydrobiologia
diapause) (Ward & Stanford, 1982). Alter
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